The GREENFLOOR ventilated concrete slab: a new-generation HVAC system

The Greenfloor solution deployed by Vinci Energies' subsidiary I.C. Entreprise reduces the amount of energy used to regulate the temperature of buildings.

Main project's drivers for reducing the greenhouse gas (GHG) emissions

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Energy and resource efficiency

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Energy Decarbonisation

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Energy efficiency improvements

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Improving efficiency in non-energy resources

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Emission removal

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Financing low-carbon issuers or disinvestment from carbon assets

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Reduction of other greenhouse gases emission

Project objectives

To improve the energy efficiency of buildings.

Developed by Vinci Energies business unit I.C. Entreprise, the Greenfloor system consists of a slab equipped with ducts that are embedded in the concrete; it is activated by ventilation air which serves as the sole heat-transfer medium, harnessing the building's inertia.

This system has several advantages:

  • Greater thermal comfort due to stable room temperature
  • Low noise level: no equipment in the dropped ceilings
  • Improved indoor air quality: fresh air supply exceeds regulation (40 cu. metres per hour per occupant vs 25 cu. metres per hour)
  • Free cooling during mid-season

The Greenfloor solution optimises ceiling height, since the ventilated active slab is no thicker than conventional slabs, while at the same time incorporating ductwork. Air is used as a heat-transfer fluid to deliver heating or cooling to the slab, which acts as a radiant ceiling.

A further benefit of this HVAC (heating-ventilation-air conditioning) technology is the energy savings it allows compared to a conventional system. Concrete has a high heat capacity ; fresh air sent into the slab at night cools it down, and cool air is redistributes during the day. Thanks to this free cooling principle, a building requires less air conditioning; AC expenditures can be reduced by 30 to 40 % compared with fan coil units or chilled beams. In winter, Greenfloor acts as an all-air system, with a minimum air change rate. Over the entire year, it is possible to achieve total savings of 10 to 15%.

Emission scope(s)

on which the project has a significant impact

Scope 1

Direct emissions generated by the company's activity.

Scope 2

Indirect emissions associated with the company's electricity and heat consumption.

Scope 3

Emissions induced (upstream or downstream) by the company's activities, products and/or services in its value chain.

Emission Removal

Carbon sinks creation, (BECCS, CCU/S, …)

Avoided Emissions

Emissions avoided by the activities, products and/or services in charge of the project, or by the financing of emission reduction projects.

Scope 3 - Reduction of grey emissions (upstream).

Less energy required to control building temperature (downstream).

  • Quantification : 150 kgCO2eq/sq. metre

Avoided Emissions - Less energy required to control building temperature. 

  • Quantification : 90 gCO2eq/sq. metre  

Grey emissions (i.e. not related to use) associated with conventional fan coil solutions can be assessed at approximately 60 gCO2eq/sq. metre, taking into account the materials used on average.

Additionally, less energy is required to control temperature in buildings equipped with the Greenfloor system. Considering the average French energy mix used for heating buildings and the associated emission factor (0.2 kgCO2eq/kWh), the Greenfloor solution can be deemed to reduce CO2 emissions by approximately 90 gCO2eq/sq. metre.

Vinci plans to equip a surface equivalent to 70,000 sq. metre/year.

Ultimately, avoided carbon emissions are expected to total 10,000 tonnes CO2/year for Vinci (scopes 1 and 3) and 6,000 tonnes CO2/year for customers (all other things being equal).

Key points

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Invested amount

2 M€

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Starting date of the project

January 2017

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Project localisation

Northern and eastern France , Grand-Est and Paris area

Project maturity level

Prototype laboratory test (TRL 7)

Real life testing (TRL 7-8)

Pre-commercial prototype (TRL 9)

Small-scale implementation

Medium to large scale implementation

Economic profitability of the project (ROI)

Short term (0-3 years)

Middle term (4-10 years)

Long term (> 10 years)

Illustrations of the project

Embedding ducts into the slabs is a fairly simple and reproducible operation. On the future VINCI headquarters project, this task was entrusted to workers in an employment-integration programme. In this sense, the project contributes to MDG 8 – Decent work and economic growth and MDG 10  – Reduced inequalities.

Gains announced (in terms of climate impact) are inherent to our solution’s design and are highly reproducible. Greater potential can be achieved through appropriate control of the system, harnessing the inertia of slabs and allowing slight temperature drifts.

The GREENFLOOR System should be considered in the very early stages of  projects:

  • Slabs need to be cast in place. The active face of the slab must not be covered by a dropped ceiling.

The incorporation of ducts into the reinforced slab may require additional design work.

As part of this project, VINCI worked with the CERIB (French Centre for Concrete Research and Studies) to validate the fire resistance of the concrete slab with embedded ducts; the results were then approved by the CSTB (French Scientific and Technical Centre for the Construction Industry).

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Contact the company carrying the project :

guillaume.rabut@vinci-energies.com

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